Amides such as acrylamide are important compounds used for various purposes, such as coagulants, paper strength agents, coating materials, agents for crude oil drilling, agents for enhanced oil (crude oil) recovery, lubricants, plasticizers, parting agents and anti-foaming agents. As the process for producing such amides, a process comprising reacting nitriles with water in the presence of a catalyst is known, and a process using a solid catalyst, a biocatalyst or a metal complex catalyst is mainly used.
As the solid catalytic process, for example, a process using a catalyst containing, copper is known (patent literatures 1 and 2), but there are problems that the raw material nitrile needs to be recycled because the conversion of nitrile to amide does not reach 100%, the amide as a product is contaminated with a slight amount of copper ion derived from the catalyst, etc.
On the other hand, as a process overcoming the defects of the solid catalytic process, having a conversion of 100% and being free from contamination with copper ion, a biocatalytic process has been used (non patent literature 1). In the biocatalytic process, however, a large amount of water is necessary in the reaction system because living organisms are used, and in order to obtain amide as crystal, a step and equipment (large amount of energy) for removing the above-mentioned large amount of water become necessary. Further, there is room for improvement in culture and refrigeration of a biocatalyst, complicated thawing conditions, method for removing a biocatalyst from the amide produced, etc.
In addition, as a process using a metal complex catalyst, for example, a process using, a platinum phosphine catalyst is known (patent literature 3). Although the platinum catalyst shows high activity, there are problems that the catalyst is expensive, the preparation thereof is complicated, etc. On the other hand, the present inventors have studied processes for synthesizing amide compounds utilizing catalytic action attributed to a combination of a ruthenium complex or an iridium complex and a phosphine compound (patent literatures 4 and 5). Also in the case of the catalyst using the combination of a ruthenium complex or an iridium complex and a phosphine compound, however, there is room for improvement in achievement of reaction under the conditions of lower temperature and smaller amount of thermal energy, yield and purity of the resulting amides (particularly acrylic amides), etc. Recently, a catalyst system in which a ruthenium complex catalyst and a surface active agent are combined has been reported, but the production efficiency (catalytic activity) of amides is extremely low, and the economical efficiency is extremely low (non patent literature 2).
In a non patent literature 3 (compound 8), a ruthenium complex having a phosphine ligand including a pentafluorobenzyl group is disclosed. However, use of the compound, particularly, use of the compound as a catalyst in the production of amides, is neither described nor suggested at all.